Sanitary piping as used in the food processing industry is primarily characterized by the requirement for corrosion resistance and stream-line fluid flow free of crevices and traps into which particulate matter that may be carried by the fluid stream might accumulate. To fill this need, the food and beverage industry makes extensive use of smooth bore sanitary piping that is almost exclusively made of stainless steel, monel or other corrosion resistant metallic alloys. These piping installations normally include a number of quick-connect/disconnect fittings to permit critical sections of the pipe to be dismantled for periodic cleaning, replacement, or inspection so that the sanitary integrity of the food processing system can be maintained.
Although stainless steel and monel pipes are usually thought to be corrosion resistant, problems have been encountered when brine and various acids are significant constituents of the fluid carried by the piping system. Certain foods such as catsup and bar-b-que sauce and those having a garlic content are also known to be troublesome. The corrosion problem is further aggravated by the periodic need to use clean-in-place solutions to remove possible pockets of accumulated organic matter. Through the combined effects of reactive food materials and such cleaning solutions, replacement of corrosion resistant piping is an on-going periodic activity.
Of course, there are several plastic materials which offer better corrosion resistance than metallic alloy pipes and which being transparent would permit in-place interior inspection without disassembly. Further, the use of plastic piping which permits the use of microwave heating of the fluid stream would permit different and more advanced methods of food processing to be employed.
The introduction of plastic pipe sections into the food processing industry has heretofore been inhibited by several factors. Sanitarians have not approved the use of solvents to glue together pipe sections in the manner commonly utilized to install ordinary household and industrial plumbing. The strict prohibitions against crevices and traps into which particulate matter carried in the fluid stream rule out the use of conventional plastic fittings. While it is conceivable that plastic fittings having the appropriate internal contours to satisfy sanitary flow requirements could be fabricated in analogous fashion to the presently available metal fittings, there are no known welding techniques avaliable for attaching such plastic fittings. The fatory casting of sanitary flow end-connections on pipe lengths also does not seem to be feasible in view of the myraid lengths and shapes of pipe runs to be supplied in practice. Accordingly, while it would appear to be extremely advantageous to employ plastic piping in sanitary-flow installations, there has not yet been devised a practical method for permitting appropriate piping connections to be made in the field.